--
-- (C) 2017-20 - ntop.org
--

-- Module to keep things in common across pools of various type

require "lua_utils"
local user_scripts = require "user_scripts"
local json = require "dkjson"

-- ##############################################

local base_pools = {}

-- ##############################################

-- A default pool id value associated to any member without pools
base_pools.DEFAULT_POOL_ID = 0

-- ##############################################

-- This is the minimum pool id which will be used to create new pools
base_pools.MIN_ASSIGNED_POOL_ID = 1

-- ##############################################

function base_pools:create(args)
   if args then
      -- We're being sub-classed
      if not args.key then
	 return nil
      end
   end

   local this = args or {key = "base"}

   setmetatable(this, self)
   self.__index = self

   return this
end

-- ##############################################

function base_pools:_get_pools_prefix_key()
   local key = string.format("ntopng.pools.%s_pools", self.key)
   -- e.g.:
   --  ntopng.pools.interface_pools
   --  ntopng.pools.snmp_device_pools
   --  ntopng.pools.network_pools

   return key
end

-- ##############################################

function base_pools:_get_pool_ids_key()
   local key = string.format("%s.pool_ids", self:_get_pools_prefix_key())
   -- e.g.:
   --  ntopng.pools.interface_pools.pool_ids

   return key
end

-- ##############################################

function base_pools:_get_next_pool_id_key()
   local key = string.format("%s.next_pool_id", self:_get_pools_prefix_key())
   -- e.g.:
   --  ntopng.pools.interface_pools.next_pool_id

   return key
end

-- ##############################################

function base_pools:_get_pool_lock_key()
   local key = string.format("%s.pool_lock", self:_get_pools_prefix_key())
   -- e.g.:
   --  ntopng.pools.interface_pools.pool_lock

   return key
end

-- ##############################################

function base_pools:_get_pool_details_key(pool_id)
   if not pool_id then
      -- A pool id is always needed
      return nil
   end

   local key = string.format("%s.pool_id_%d.details", self:_get_pools_prefix_key(), pool_id)

   return key
end

-- ##############################################

function base_pools:_assign_pool_id()
   local next_pool_id_key = self:_get_next_pool_id_key()

   -- Atomically assign a new pool id
   local next_pool_id = ntop.incrCache(next_pool_id_key)

   -- Make sure the id equals at least the minimum required id
   while next_pool_id < base_pools.MIN_ASSIGNED_POOL_ID do
      next_pool_id = ntop.incrCache(next_pool_id_key)
   end

   -- Add the atomically assigned pool id to the set of current pool ids (set wants a string)
   ntop.setMembersCache(self:_get_pool_ids_key(), string.format("%d", next_pool_id))

   return next_pool_id
end


-- ##############################################

-- @brief Returns an array with all the currently assigned pool ids
function base_pools:_get_assigned_pool_ids()
   local res = {}

   local cur_pool_ids = ntop.getMembersCache(self:_get_pool_ids_key())
   for _, cur_pool_id in pairs(cur_pool_ids) do
      cur_pool_id = tonumber(cur_pool_id)

      if cur_pool_id ~= base_pools.DEFAULT_POOL_ID then
	 -- the default pool id is never returned,
	 -- it's a meta-pool without members
	 res[#res + 1] = cur_pool_id
      end
   end

   return res
end

-- ##############################################

function base_pools:_lock()
   local max_lock_duration = 5 -- seconds
   local max_lock_attempts = 5 -- give up after at most this number of attempts
   local lock_key = self:_get_pool_lock_key()

   for i = 1, max_lock_attempts do
      local value_set = ntop.setnxCache(lock_key, "1", max_lock_duration)

      if value_set then
	 return true -- lock acquired
      end

      ntop.msleep(1000)
   end

   return false -- lock not acquired
end

-- ##############################################

function base_pools:_unlock()
   ntop.delCache(self:_get_pool_lock_key())
end

-- ##############################################

-- @brief Persist pool details to disk. Possibly assign a pool id
-- @param pool_id The pool_id of the pool which needs to be persisted. If nil, a new pool id is assigned
function base_pools:_persist(pool_id, name, members, configset_id)
   -- self:cleanup()

   local pool_details_key = self:_get_pool_details_key(pool_id)
   local pool_details = {
      name = name,
      members = members,
      configset_id = configset_id
   }
   ntop.setCache(pool_details_key, json.encode(pool_details))

   -- Return the assigned pool_id
   return pool_id
end

-- ##############################################

function base_pools:add_pool(name, members, configset_id)
   local pool_id

   local locked = self:_lock()

   if locked then
      if name and members and configset_id then
	 local checks_ok = true

	 -- Check if duplicate names exist
	 local same_name_pool = self:get_pool_by_name(name)
	 if same_name_pool then checks_ok = false end

	 -- Check if members are valid
	 if not self:are_valid_members(members) then checks_ok = false end

	 -- Check if members do not belong to any other pool
	 if checks_ok then
	    for _, member in pairs(members) do
	       local cur_pool = self:get_pool_by_member(member)

	       if cur_pool then
		  -- Member already existing in another pool
		  checks_ok = false
		  break
	       end
	    end
	 end

	 -- Check if the configset_id is valid
	 if checks_ok then
	    local available_configsets = self:get_available_configset_ids()

	    if not available_configsets[configset_id] then
	       -- Configset id not found
	       checks_ok = false
	    end
	 end

	 if checks_ok then
	    -- All the checks have succeeded
	    -- Now that everything is ok, the id can be assigned and the pool can be persisted with the assigned id
	    pool_id = self:_assign_pool_id()

	    self:_persist(pool_id, name, members, configset_id)
	 end
      end

      self:_unlock()
   end

   return pool_id
end

-- ##############################################

function base_pools:edit_pool(pool_id, new_name, new_members, new_configset_id)
   local ret = false

   local locked = self:_lock()

   -- Make sure the pool exists
   local cur_pool_details = self:get_pool(pool_id)

   -- If here, pool_id has been found
   if locked then
      if not new_members then
	 -- In case members have not been sumbitted, new_members
	 -- are assumed to be the existing members
	 new_members = cur_pool_details["members"]
      end

      if cur_pool_details and new_name and new_members and new_configset_id then
	 local checks_ok = true

	 -- Check if new_name is not the name of any other existing pool
	 local same_name_pool = self:get_pool_by_name(new_name)
	 if same_name_pool and same_name_pool.pool_id ~= pool_id then checks_ok = false end

	 -- Check if members are valid
	 if checks_ok and not self:are_valid_members(new_members) then checks_ok = false end

	 -- Check if none of new_members belongs to any other exsiting pool
	 if checks_ok then
	    for _, new_member in pairs(new_members) do
	       local new_member_pool = self:get_pool_by_member(new_member)

	       if new_member_pool and new_member_pool["pool_id"] ~= pool_id then
		  -- Member already existing in another pool
		  checks_ok = false
		  break
	       end
	    end
	 end

	 -- Check if the configset_id is valid
	 if checks_ok then
	    local available_configsets = self:get_available_configset_ids()

	    if not available_configsets[new_configset_id] then
	       -- Configset id not found
	       checks_ok = false
	    end
	 end

	 if checks_ok then
	    -- If here, all checks are valid and the pool can be edited
	    self:_persist(pool_id, new_name, new_members, new_configset_id)

	    -- Pool edited successfully
	    ret = true
	 end
      end

      self:_unlock()
   end

   return ret
end

-- ##############################################

function base_pools:delete_pool(pool_id)
   local ret = false

   local locked = self:_lock()

   if locked then
      -- Make sure the pool exists
      local cur_pool_details = self:get_pool(pool_id)

      if cur_pool_details then
	 -- Remove the key with all the pool details (e.g., with members, and configset_id)
	 ntop.delCache(self:_get_pool_details_key(pool_id))

	 -- Remove the pool_id from the set of all currently existing pool ids
	 ntop.delMembersCache(self:_get_pool_ids_key(), string.format("%d", pool_id))

	 ret = true
      end

      self:_unlock()
   end

   return ret
end

-- ##############################################

-- @brief Returns all the defined pools. Pools are returned in a lua table with pool ids as keys
function base_pools:get_all_pools()
   local cur_pool_ids = self:_get_assigned_pool_ids()
   local res = {}

   for _, pool_id in pairs(cur_pool_ids) do
      local pool_details = self:get_pool(pool_id)

      if pool_details then
	 res[#res + 1] = pool_details
      end
   end

   return res
end

-- ##############################################

function base_pools:get_pool(pool_id)
   local pool_details
   local pool_details_key = self:_get_pool_details_key(pool_id)

   -- Attempt at retrieving the pool details key and at decoding it from JSON
   if pool_details_key then
      local pool_details_str = ntop.getCache(pool_details_key)
      pool_details = json.decode(pool_details_str)

      if pool_details then
	 -- Add the integer pool id
	 pool_details["pool_id"] = tonumber(pool_id)

	 if pool_details["members"] then
	    -- Add a new table with member details
	    -- Table keys are members, table values are member details
	    pool_details["member_details"] = {}
	    for _, member in pairs(pool_details["members"]) do
	       pool_details["member_details"][member] = self:get_member_details(member)
	    end
	 end

	 if pool_details["configset_id"] then
	    local configset_id = pool_details["configset_id"]
	    local config_sets = user_scripts.getConfigsets()

	    -- Add a new (small) table with configset details, including the name
	    if config_sets[configset_id] and config_sets[configset_id]["name"] then
	       pool_details["configset_details"] = {name = config_sets[configset_id]["name"]}
	    end
	 end
      end
   end

   -- Upon success, pool details are returned, otherwise nil
   return pool_details
end

-- ##############################################

function base_pools:get_pool_by_name(name)
   local cur_pool_ids = self:_get_assigned_pool_ids()

   for _, pool_id in pairs(cur_pool_ids) do
      local pool_details = self:get_pool(pool_id)

      if pool_details and pool_details["name"] and pool_details["name"] == name then
	 return pool_details
      end
   end

   return nil
end

-- ##############################################

-- @brief Returns the pool to which `member` is currently bound to, or nil if `member` is not bound to any pool
function base_pools:get_pool_by_member(member)
   local assigned_members = self:get_assigned_members()

   if assigned_members[member] then
      return self:get_pool(assigned_members[member]["pool_id"])
   end

   return nil
end

-- ##############################################

function base_pools:get_pools_by_configset_id(configset_id)
   local cur_pool_ids = self:_get_assigned_pool_ids()
   local res = {}

   for _, pool_id in pairs(cur_pool_ids) do
      local pool_details = self:get_pool(pool_id)

      if pool_details and pool_details["configset_id"] and pool_details["configset_id"] == configset_id then
	 res[#res + 1] = pool_details
      end
   end

   return res
end

-- ##############################################

-- @brief Returns a flattened table with pool_member->pool_id pairs
function base_pools:get_assigned_members()
   local cur_pool_ids = self:_get_assigned_pool_ids()
   local res = {}

   for _, pool_id in pairs(cur_pool_ids) do
      local pool_details = self:get_pool(pool_id)

      if pool_details and pool_details["members"] then
	 for _, member in pairs(pool_details["members"]) do
	    res[member] = {pool_id = tonumber(pool_id), configset_id = pool_details["configset_id"]}
	 end
      end
   end

   return res
end

-- ##############################################

function base_pools:cleanup()
   -- Delete pool details
   local cur_pool_ids = self:_get_assigned_pool_ids()
   for _, pool_id in pairs(cur_pool_ids) do
      self:delete_pool(pool_id)
   end

   local locked = self:_lock()
   if locked then
      -- Delete pool ids
      ntop.delCache(self:_get_pool_ids_key())
      ntop.delCache(self:_get_next_pool_id_key())

      self:_unlock()
   end
end

-- ##############################################

-- @brief Returns a boolean indicating whether the member is a valid pool member
function base_pools:is_valid_member(member)
   local all_members = self:get_all_members()
   return all_members[member] ~= nil
end

-- ##############################################

-- @brief Returns a boolean indicating whether the array of members passed contains all valid members
function base_pools:are_valid_members(members)
   for _, member in pairs(members) do
      if not self:is_valid_member(member) then
	 return false
      end
   end

   return true
end

-- ##############################################

-- @brief Parses members submitted via HTTP (validated as `pool_members` in `http_lint.lua`) into a table of members
function base_pools:parse_members(members_string)
   local members = {}

   if isEmptyString(members_string) then
      return members
   end

   -- Unfold the members csv
   members = members_string:split(",") or {members_string}

   return members
end

-- ##############################################

-- @brief Returns available members which don't already belong to any defined pool
function base_pools:get_available_members()
   local assigned_members = self:get_assigned_members()
   local all_members = self:get_all_members()

   local res = {}
   for member, member_details in pairs(all_members) do
      --      tprint("checking.."..member)
      --      tprint(member)
      if not assigned_members[member] then
	 res[member] = member_details
      end
   end

   return res
end

-- ##############################################

function base_pools:bind_member(member, pool_id)
   local ret = false

   if not self:is_valid_member(member) then
      return ret
   end

   local locked = self:_lock()

   if locked then
      -- REMOVE the member if assigned to another pool
      local assigned_members = self:get_assigned_members()
      if assigned_members[member] then
	 local cur_pool = self:get_pool(assigned_members[member]["pool_id"])

	 if cur_pool["pool_id"] == pool_id then
	    -- If the current pool id equals the new pool id, there's nothing to do and it is just safe to return
	    ret = true
	 elseif cur_pool then
	    -- New members are all pool members except for the member which is being removed
	    local new_members = {}
	    for _, cur_member in pairs(cur_pool["members"]) do
	       if cur_member ~= member then
		  new_members[#new_members + 1] = cur_member
	       end
	    end

	    -- Persist the existing pool without the removed `member`
	    self:_persist(cur_pool["pool_id"], cur_pool["name"], new_members, cur_pool["configset_id"])
	 end
      end

      -- ASSIGN the member to the pool with `pool_id`
      -- Note: If the pool_id is base_pools.DEFAULT_POOL_ID, then `member` is not associated to any pool, it's safe to just return
      if not ret then
	 if pool_id == base_pools.DEFAULT_POOL_ID then
	    ret = true
	 else
	    local bind_pool = self:get_pool(pool_id)
	    if bind_pool then
	       -- New members are all pool members plus the member which is being bound
	       local bind_pool_members = bind_pool["members"]
	       bind_pool_members[#bind_pool_members + 1] = member

	       -- Persist the pool with the new `member`
	       self:_persist(bind_pool["pool_id"], bind_pool["name"], bind_pool_members, bind_pool["configset_id"])

	       -- Bind has executed successfully
	       ret = true
	    end
	 end
      end

      self:_unlock()
   end

   return ret
end

-- ##############################################

-- @brief Unbind a `configset_id` from all pools which are currently using it, and sets them the defauls configset.
function base_pools:unbind_all_configset_id(configset_id)
   configset_id = tonumber(configset_id)

   if not configset_id then
      -- Invalid argument
      return
   end

   local locked = self:_lock()

   if locked then
      local all_pools = self:get_all_pools()

      for _, pool in pairs(all_pools) do
	 if pool["configset_id"] == configset_id then
	    -- Rewrite the pool using the default configset id
	    self:_persist(pool["pool_id"], pool["name"], pool["members"], user_scripts.DEFAULT_CONFIGSET_ID)
	 end
      end

      self:_unlock()
   end
end

-- ##############################################

-- @brief Returns available confset ids which can be added to a pool
function base_pools:get_available_configset_ids()
   -- Currently, confset_ids are shared across pools of all types
   -- so all the confset_ids can be returned here without distinction
   local config_sets = user_scripts.getConfigsets()
   local res = {}

   for _, configset in pairs(config_sets) do
      res[configset.id] = {configset_id = configset.id, configset_name = configset.name}
   end

   return res
end

-- ##############################################

-- @brief Cached `assigned_pool_members` are read and the configset_id associated to `member` is returned
-- @param assigned_pool_members A table obtained calling self:get_assigned_members()
-- @param member a valid pool member
-- @return The configset_id found for `member` or the default configset_id
function base_pools:get_configset_id(member)
   if not self.assigned_pool_members then
      -- Cache it as class member
      self.assigned_pool_members = self:get_assigned_members()
   end

   if self.assigned_pool_members[member] and self.assigned_pool_members[member]["configset_id"] then
      return self.assigned_pool_members[member]["configset_id"]
   end

   return user_scripts.DEFAULT_CONFIGSET_ID
end

-- ##############################################

return base_pools